An internal combustion engine may be used as a drive for motor vehicles. Within the context of the present disclosure, the expression “internal combustion engine” encompasses Otto-cycle engines and diesel engines but also hybrid internal combustion engines, which utilize a hybrid combustion process, and hybrid drives which comprise not only the internal combustion engine but also an electric machine which is connectable in terms of drive to the internal combustion engine and which receives power from the internal combustion engine or which, as a switchable auxiliary drive, outputs power in addition.
Internal combustion engines have a cylinder block and at least one cylinder head which are connectable to one another or connected to one another in order to form the individual cylinders, that is to say combustion chambers. The individual components will be discussed briefly below.
The cylinder head may hold the control elements, and in the case of an overhead camshaft, to hold the valve drives in their entirety. During the charge exchange, the combustion gases are discharged via the at least one outlet opening and the charging of the combustion chamber takes place via the at least one inlet opening of the at least one cylinder. To control the charge exchange, in four-stroke engines, use is made almost exclusively of lifting valves as control elements, which lifting valves perform an oscillating lifting movement during the operation of the internal combustion engine and which lifting valves open and close the inlet opening and outlet opening in this way. The valve actuating mechanism used for the movement of a valve, including the valve itself, is referred to as the valve drive.
In applied-ignition internal combustion engines, an ignition device may also be arranged in the cylinder head, and furthermore in the case of direct-injection internal combustion engines, the injection device may be arranged in the cylinder head. To form a functional connection, which seals off the combustion chambers, between the cylinder head and the cylinder block, an adequately large number of adequately large bores may be provided.
To hold the pistons or the cylinder liners, the cylinder block has a corresponding number of cylinder bores. The piston of each cylinder of an internal combustion engine is guided in an axially movable manner along the cylinder longitudinal axis in a cylinder barrel and, together with the cylinder barrel and the cylinder head, delimits the combustion chamber of a cylinder. Here, the piston crown forms a part of the combustion chamber inner wall, and, together with the piston rings, seals off the combustion chamber with respect to the cylinder block or the crankcase, such that substantially no combustion gases or no combustion air pass(es) into the crankcase, and substantially no oil passes into the combustion chamber.
The pistons serve to transmit the gas forces generated by the combustion to the crankshaft. For this purpose, each piston is articulatedly connected by means of a piston pin to a connecting rod, which in turn is movably mounted on the crankshaft.
The crankshaft which is mounted in the crankcase absorbs the connecting rod forces, which are composed of the gas forces as a result of the fuel combustion in the combustion chamber and the inertia forces as a result of the non-uniform movement of the engine parts. Here, the reciprocating movement of the pistons is transformed into a rotating rotational movement of the crankshaft. The crankshaft transmits the torque to the drivetrain. A part of the energy transmitted to the crankshaft is used for driving auxiliary units such as the oil pump and the alternator, or serves for driving the camshaft and therefore for actuating the valve drives.
Generally, and within the context of the present disclosure, the upper crankcase half is formed by the cylinder block. The crankcase is generally complemented by the lower crankcase half which can be mounted on the upper crankcase half and which serves as an oil pan.
The cylinder block of an internal combustion engine is a thermally and mechanically highly loaded component, wherein the demands on the cylinder block increase. In this context, it may be taken into consideration that internal combustion engines may be supercharged—by means of exhaust-gas turbocharger or mechanical supercharger—in order to lower fuel consumption, that is to say improve efficiency. As a result, it is in particular the case that the thermal load on the internal combustion engine and on the cylinder block increases, such that increased demands may be placed on the cooling arrangement, and measures may be implemented which reliably prevent thermal overloading of the internal combustion engine.
It is fundamentally possible for the engine cooling arrangement to take the form of an air-type cooling arrangement or a liquid-type cooling arrangement. In the case of the air-type cooling arrangement, the internal combustion engine is provided with a fan, wherein the dissipation of heat takes place by means of an air flow conducted over the surface of the cylinder head and of the cylinder block.
On account of the higher heat capacity of liquids in relation to air, it is possible for significantly greater quantities of heat to be dissipated using a liquid-type cooling arrangement than is possible using an air-type cooling arrangement. For this reason, internal combustion engines may be equipped with a liquid-type cooling arrangement.
The internal combustion engine to which the present disclosure relates also has a liquid-type cooling arrangement, wherein at least the cylinder block is equipped with a liquid-type cooling arrangement.
A liquid-type cooling arrangement demands that the internal combustion engine or the cylinder block be equipped with at least one integrated coolant jacket, which conducts the coolant through the cylinder block. The heat which is released to the coolant is extracted from the coolant again for example in a heat exchanger, which may be arranged in the front-end region of the vehicle.
The heat may not initially be conducted to the block surface in order to be dissipated, as is the case in an air-type cooling arrangement, but rather is discharged to the coolant already in the interior of the cylinder block. Here, the coolant may be delivered by means of a pump arranged in the coolant circuit, such that said coolant circulates. The heat which is discharged to the coolant is thereby discharged from the interior of the cylinder block, and is extracted from the coolant again outside the cylinder block, for example by means of a heat exchanger and/or in some other way.
A coolant may comprise a water-glycol mixture provided with additives. In relation to other coolants, water may be non-toxic, readily available, and cheap, and furthermore has a high heat capacity, for which reason water is suitable for the extraction and dissipation of large amounts of heat.
Like the cylinder block, the cylinder head may also be equipped with one or more coolant jackets. The cylinder head is generally the thermally more highly loaded component because, by contrast to the cylinder block, the head is provided with exhaust-gas-conducting lines, and the combustion chamber walls which are integrated in the head are exposed to hot exhaust gas for longer than the cylinder barrels provided in the cylinder block. Furthermore, the cylinder head has a lower component mass than the block.
Equipping the cylinder block with a liquid-type cooling arrangement and at least one coolant jacket has the effect, in an internal combustion engine according to previous examples, that large temperature gradients arise in the block during operation, in particular in a web region, that is to say in the region between two adjacent cylinders, which may also referred to as bore bridge. This is also owing to the fact that the cooling arrangement according to the previous examples is designed not in accordance with demand but rather with regard to the method of production of the cylinder block, which is generally produced in a casting process, whereby the arrangement and shaping of the coolant jackets is heavily influenced and limited. That is to say, a manufacturing process (e.g., the casting process) currently implemented by those skilled in the art may limit cooling in the web region due to the cooling arrangement not being sufficiently incorporated into the web region.
The large temperature differences in the cylinder block may result in greater or lesser thermal distortion of the cylinder barrel of a cylinder. This so-called bore distortion has numerous disadvantageous effects in practice.
According to previous examples, to reduce the bore distortion, slots and/or relatively small bores are formed in the web region by cutting machining of the cylinder block. This measure however leads only to a slight improvement, because it is not possible to machine the entire region between two adjacent cylinders. Furthermore, the highly loaded block is weakened in terms of its strength and durability. As such, these slots do not solve the bore distortion described above.
In order that the piston in interaction with the cylinder barrel and the piston rings can seal off the combustion chamber with respect to the crankcase in an effective manner despite bore distortion, the preload forces of the rings are, according to the previous examples, increased, though this disadvantageously likewise increases the friction or friction losses of the internal combustion engine.
It is sought to minimize the friction losses of an internal combustion engine in order to reduce the fuel consumption and thus also the pollutant emissions.
The inventors have found a solution to at least partially solve the problems described above. In one example, the issues described above may be addressed by a liquid-cooled internal combustion engine having at least one cylinder head with at least one cylinder, at least one cylinder block, which is connected to the at least one cylinder head and which serves as an upper crankcase half, for accommodating at least one piston, each cylinder comprising a combustion chamber which is formed jointly by the cylinder-specific piston, by a cylinder barrel and by the at least one cylinder head, the piston being displaceable in translational fashion along a cylinder longitudinal axis, and the cylinder block being equipped with a liquid-type cooling arrangement. The internal combustion engine further comprising where the cylinder block is equipped with at least one integrated coolant duct for forming a liquid-type cooling arrangement, at least one coolant duct meandering so as to form loops along the cylinder longitudinal axis and at a distance from the cylinder barrel, and the density of the loops increasing in the direction of the at least one cylinder head.
By contrast to the previous examples, the cylinder block of an internal combustion engine according to the disclosure does not have a large-area coolant jacket which covers or surrounds the at least one cylinder barrel at least in regions and which promotes production by means of casting.
Rather, to form the liquid-type cooling arrangement, at least one coolant duct may be provided or integrated in the cylinder block. Here, at least one coolant duct may be led around a cylinder barrel, specifically such that said duct meanders so as to form loops along the cylinder longitudinal axis (e.g., axis about which the piston oscillates) and at a distance from the cylinder barrel. The duct loops around the cylinder barrel over an angle γ. This production of the liquid-type cooling arrangement, in which ducts can be led through the cylinder block in accordance with the actual cooling demand, is made possible by producing the block using an additive manufacturing process, in the case of which the cylinder block is built up in layered fashion.
Consequently, allowance can also be made for the fact that a cylinder block is thermally particularly highly loaded in the web region, and the thermal loading basically increases in the direction of the cylinder head, that is to say increases along the cylinder longitudinal axis toward the cylinder head.
According to the disclosure, therefore, it is also the case that the density of the loops increases in the direction of the at least one cylinder head. In the context of the present disclosure, a loop refers to a duct section which comprises two limbs and an intermediate piece connecting said two limbs, wherein the limbs generally run transversely with respect to the cylinder longitudinal axis, and the intermediate piece generally runs parallel to the cylinder longitudinal axis. For the coolant, there is thus a resulting main delivery direction along the cylinder longitudinal axis, toward the cylinder head or away from the cylinder head. Additionally or alternatively, density of loops may refer to one or more of a number of loops and a volume of the loops.
If the density of the loops increases, this means that the number of loops or the number of duct sections, which form the loops, per unit of distance increases in the direction of the cylinder longitudinal axis. With increasing density of the loops, the limb-like duct sections are at a smaller distance from one another, whereby the cooling power likewise increases.
The internal combustion engine according to the disclosure achieves at least a partial solution to the issues described above, specifically that of providing a liquid-cooled internal combustion engine which is improved with regard to the thermally induced bore distortion in the cylinder block.
Embodiments of the liquid-cooled internal combustion engine may comprise at least one coolant duct meanders so as to form U-shaped loops along the cylinder longitudinal axis and at a distance from the cylinder barrel.
The U-shaped design of the loops makes allowance for the fact that, according to the disclosure, a loop comprises two limbs and an intermediate piece connecting said two limbs. The limbs preferably run transversely with respect to the cylinder longitudinal axis, and the intermediate piece may extend parallel to the cylinder longitudinal axis.
Embodiments of the liquid-cooled internal combustion engine may comprise at least one coolant duct meanders so as to form loops along the cylinder longitudinal axis and at a distance from the cylinder barrel and, in so doing, loops around the cylinder barrel over an angle γ.
In configuring the magnitude of the loop angle γ, it is necessary to take into consideration the aim that it is sought to achieve by means of the liquid-type cooling arrangement, in particular also which region of the cylinder block a duct is arranged in and what possibilities are afforded by said region or what conditions are demanded of the cooling arrangement by the thermal load in said region.
In this context, embodiments of the liquid-cooled internal combustion engine may be comprise in which, for the angle γ, the following applies: γ≤360°. In this embodiment, a duct may loop around the cylinder barrel in its entirety, that is to say over its full circumference.
In this context, embodiments of the liquid-cooled internal combustion engine may also comprise in which, for the angle γ, the following applies: γ≤270°. This embodiment may be suitable for example for an outer cylinder of an in-line engine, wherein the duct is arranged or runs predominantly on the side averted from the adjacent inner cylinder.
In this context, embodiments of the liquid-cooled internal combustion engine may likewise comprise in which, for the angle γ, the following applies: γ≤180°. This embodiment may be suitable for example for an inner cylinder of an in-line engine, wherein the duct is arranged or runs between the two bore bridges with the adjacent cylinders. The same also applies to the following embodiment.
Specifically, in this context, embodiments of the liquid-cooled internal combustion engine may also comprise in which, for the angle γ, the following applies: γ≤90°. This embodiment may furthermore also be suitable for the cooling of a bore bridge, that is to say for the cooling of the region between adjacent cylinders, which is thermally particularly highly loaded and therefore also has the greatest cooling demand. The same also applies to the following embodiment.
In this context, embodiments of the liquid-cooled internal combustion engine may comprise in which, for the angle γ, the following applies: γ≤60°. This embodiment may also be suitable for the cooling of the bore bridge between two adjacent cylinders.
In the case of liquid-cooled internal combustion engines having at least one cylinder head with at least two cylinders, embodiments may therefore also comprise in which at least one integrated coolant duct runs and meanders between two adjacent cylinders in the web region.
In this context, embodiments of the liquid-cooled internal combustion engine may comprise in which two integrated coolant ducts run and meander between two adjacent cylinders in the web region.
Embodiments of the liquid-cooled internal combustion engine may comprise in which the cylinder block is equipped with at least two integrated coolant ducts for forming a liquid-type cooling arrangement. Then, a cylinder of a multi-cylinder internal combustion engine may be equipped with two or more coolant ducts, for example one duct which meanders in the web region and has a relatively small loop angle γ, and one duct which circumferentially loops around the cylinder barrel outside the web region over a relatively large angle γ.
In this context, embodiments of the liquid-cooled internal combustion engine may comprise in which at least two integrated coolant ducts have a separate, independent coolant supply. This embodiment may acknowledge that different regions of the block have different levels of cooling demand.
A separate, independent coolant supply makes it possible, for example, to realize a higher coolant throughput through a duct which meanders in the web region, and a lower coolant throughput through a duct which loops around the cylinder barrel outside the web region. In addition to a variation of the coolant throughput, it is also possible to realize a different coolant temperature, and possibly to use a different coolant; for example water and oil.
Embodiments of the liquid-cooled internal combustion engine may comprise in which the cylinder barrel of a cylinder is formed as a cylinder bore of the cylinder block.
However, embodiments of the liquid-cooled internal combustion engine may also comprise in which the cylinder barrel of a cylinder is a cylinder liner which is inserted into the cylinder block.
The above embodiments may differ by the fact that the piston is, on the one hand, received and mounted directly in the cylinder block, with a cylinder bore serving for this purpose, and on the other hand, a liner is provided for receiving the piston, wherein said liner is received in the block.
In the context of the present disclosure, the expression “cylinder barrel” is a generic term under which the designations or embodiments “cylinder bore” and “cylinder liner” can be subsumed.
The disclosure further comprises a method, specifically that of specifying a method for producing a cylinder block of an internal combustion engine of a type described above, is achieved by way of a method which is distinguished by the fact that the cylinder block is produced by means of an additive manufacturing method, in which the cylinder block is built up in layered fashion.
That which has already been stated with regard to the internal combustion engine according to the disclosure also applies to the method according to the disclosure.
Embodiments of the method may comprise where the cylinder block is produced at least inter alia by means of 3D printing. It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.